Driving method for liquid crystal device, liquid crystal device, and electronic device

ABSTRACT

A driving method for a liquid crystal device, which has a first electrode, a second electrode, and a third electrode for trapping ions, includes applying AC signals having the same frequency but whose phases in an amount of time corresponding to a single cycle are shifted relative to each other to the first electrode, the second electrode, and the third electrode, respectively, so that the distribution of an electrical field produced between the first electrode, the second electrode, and the third electrode is scrolled from the first electrode to the third electrode over time.

BACKGROUND

1. Technical Field

The present invention relates to driving methods for liquid crystaldevices, liquid crystal devices, and electronic devices that includesuch liquid crystal devices.

2. Related Art

A liquid crystal device includes a liquid crystal panel in which aliquid crystal layer is interposed between two substrates. When light isincident on such a liquid crystal device, a liquid crystal material, anorientation layer, and so on that configure the liquid crystal panelreact photochemically with the incident light, and ionic impurities aresometimes produced by the reaction. It is furthermore known that ionicimpurities diffuse into the liquid crystal layer from sealants, sealingmembers, and so on during the production of such a liquid crystal panel.In particular, the luminous density of the incident light is higher in aliquid crystal device such as an optical modulation unit (a light valve)that is used in a projection-type display apparatus (a projector) thanin a direct-view liquid crystal device, and it is thus necessary tosuppress the influence that ionic impurities have on the display.

As a technique for suppressing the influence of ionic impurities on adisplay, JP-A-2008-58497, for example, discloses a driving method for aliquid crystal display device in which peripheral electrodes configuredof a plurality of adjacent electrodes are provided in a peripheralregion surrounding a pixel region in at least one substrate in a pair ofsubstrates between which a liquid crystal layer is interposed, andvoltage values of driving voltages applied between adjacent electrodesin the peripheral electrodes vary.

According to the driving method for a liquid crystal display devicedisclosed in JP-A-2008-58497, a horizontal electrical field is producedbetween adjacent electrodes in the peripheral electrodes, which producesa force that causes ionic impurities to move in addition to a flowproduced by minute amounts of sway in the liquid crystals; as a result,ionic impurities that move from the pixel region can be quickly movedoutside of the pixel region, and display problems caused by the ionicimpurities, such as burn-in, can be prevented.

However, according to the liquid crystal display device and the drivingmethod thereof disclosed in the aforementioned JP-A-2008-58497, thedirection of an electric flux line produced by applying an AC voltagebetween adjacent electrodes A and B in the peripheral electrodes includea direction from the electrode A, which is closer to the pixel region,toward the electrode B, as well as a direction from the electrode B,which is farther from the pixel region, toward the electrode A. Ionicimpurities have a positive or a negative polarity, and as such it ispossible to pull the ionic impurities using the electrical fieldproduced between the adjacent electrodes A and B; however, it cannot besaid that the effect of sweeping off the ionic impurities from the pixelregion to the outside thereof is consistently sufficient. There has thusbeen a problem that the influence ionic impurities contained in theliquid crystal layer have on the display cannot necessarily besufficiently suppressed.

SUMMARY

Having been conceived in order to solve at least part of theaforementioned problems, the invention is to provide driving methods forliquid crystal devices, liquid crystal devices, and electronic devicesthat can be implemented as the following aspects or applicationexamples.

First Application Example

A liquid crystal device driving method according to an aspect of theinvention is a driving method for a liquid crystal device including afirst substrate and a second substrate that are disposed opposing eachother and are laminated to each other using a sealant, a liquid crystallayer interposed between the first substrate and the second substrate, apixel electrode provided in a display region of the first substrate, anopposing electrode provided in the first substrate or the secondsubstrate so as to oppose the pixel electrode, and a first electrodethat, when viewed from above, is provided between the display region andthe sealant and to which a first potential is supplied, a secondelectrode that, when viewed from above, is provided between the firstelectrode and the sealant and to which a second potential is supplied,and a third electrode that, when viewed from above, is provided betweenthe second electrode and the sealant and to which a third potential issupplied, the first electrode, the second electrode, and the thirdelectrode being provided in the first substrate or the second substrate.The driving method comprises applying AC signals having the samefrequency to the first electrode, the second electrode, and the thirdelectrode, respectively, so that the second potential shifts from apositive-polarity or a reference potential to a negative-polarity afterthe first potential has shifted from the positive-polarity or thereference potential to the negative-polarity but before the firstpotential shifts to the reference potential or the positive-polarity,the third potential shifts from the positive-polarity or the referencepotential to the negative-polarity after the second potential hasshifted to the negative-polarity but before the second potential shiftsto the reference potential or the positive-polarity, the secondpotential shifts from the negative-polarity or the reference potentialto the positive-polarity after the first potential has shifted from thenegative-polarity or the reference potential to the positive-polaritybut before the first potential shifts to the reference potential or thenegative-polarity, and the third potential shifts from thenegative-polarity or the reference potential to the positive-polarityafter the second potential has shifted from the negative-polarity or thereference potential to the positive-polarity but before the secondpotential shifts to the reference potential or the negative-polarity.

According to the liquid crystal device driving method according to thisaspect of the invention, AC signals whose phases are shifted are appliedto the first electrode, the second electrode, and the third electrode,in that order, in an amount of time corresponding to a single cycle inwhich the first potential shifts from the reference potential, to thepositive-polarity, and to the negative-polarity. Accordingly, thedirection of an electrical field (electric flux line) produced betweenthe electrodes changes from the first electrode, which is closest to thedisplay region, toward the second electrode, and then from the secondelectrode toward the third electrode, as time passes. Due to theelectrical field direction shifting, ionic impurities are first pulledto the first electrode, and are then pulled to the second electrode andthe third electrode. In other words, a liquid crystal device drivingmethod capable of effectively sweeping ionic impurities within theliquid crystal layer away from the display region can be provided.

It is preferable that, in the liquid crystal device driving method inthe above example, a frequency f (Hz) of the AC signals fulfill thefollowing formula:f≦2μV _(E) /np ²

Here, μ represents a degree of movement (m²/V·s) of ionic impurities inthe liquid crystal layer, V_(E) represents an effective voltage (V) ofthe AC signals, n represents a number of electrodes to which the ACsignals are applied, and p represents a pitch (m) at which theelectrodes to which the AC signals are applied are disposed.

A movement velocity of the ionic impurities that move between theelectrodes to which the AC signals have been applied, or in other words,an amount of time required for the movement, depends on a degree ofmovement of the ionic impurities and an essential potential differencebetween the electrodes, and is in an inverse proportion to the distancebetween the electrodes. Accordingly, it is preferable to match themanner in which the electrical field is produced between the electrodesto the movement velocity of the ionic impurities.

According to this method, the frequency f (Hz) of the AC signals is thesame or lower than the velocity (amount of time) at which the ionicimpurities move a distance corresponding to the pitch at which theelectrodes are disposed, and thus the ionic impurities within the liquidcrystal layer can be swept outside of the display region with certainty.

It is preferable that, in the liquid crystal device driving method inthe above example, the AC signals applied to the first electrode, thesecond electrode, and the third electrode, respectively, have the samewaveform.

The “same waveform” refers to waveforms whose phases are different butwhose waveforms are substantially the same.

According to this method, it is not necessary to generate AC signalshaving different waveforms, and thus the configuration of a drivingcircuit can be simplified.

It is preferable that, in the liquid crystal device driving method inthe above example, the AC signals have a potential of three or morevalues.

According to this method, the potentials applied to the first electrode,the second electrode, and the third electrode, respectively, have threeor more values, and thus the electrical field can be caused to movebetween the electrodes smoothly.

It is preferable that, in the liquid crystal device driving method inthe above example, the AC signals be square waves.

According to this method, an electrical field whose intensity is stablecan be produced between adjacent electrodes among the first electrode,the second electrode, and the third electrode, and thus the ionicimpurities can be more effectively swept away. Furthermore, it is easierto generate the AC signals than when using, for example, an analogsignal such as a sine wave.

Second Application Example

A liquid crystal device according to another aspect of the inventionincludes a first substrate and a second substrate that are disposedopposing each other and are laminated to each other using a sealant, aliquid crystal layer interposed between the first substrate and thesecond substrate, a pixel electrode provided in a display region of thefirst substrate, an opposing electrode provided in the first substrateor the second substrate so as to oppose the pixel electrode, and a firstelectrode that, when viewed from above, is provided between the displayregion and the sealant and to which a first potential is supplied, asecond electrode that, when viewed from above, is provided between thefirst electrode and the sealant and to which a second potential issupplied, and a third electrode that, when viewed from above, isprovided between the second electrode and the sealant and to which athird potential is supplied, the first electrode, the second electrode,and the third electrode being provided in the first substrate or thesecond substrate. Here, AC signals having the same frequency are appliedto the first electrode, the second electrode, and the third electrode,respectively, so that the second potential shifts from apositive-polarity or a reference potential to a negative-polarity afterthe first potential has shifted from the positive-polarity or thereference potential to the negative-polarity but before the firstpotential shifts to the reference potential or the positive-polarity,the third potential shifts from the positive-polarity or the referencepotential to the negative-polarity after the second potential hasshifted to the negative-polarity but before the second potential shiftsto the reference potential or the positive-polarity, the secondpotential shifts from the negative-polarity or the reference potentialto the positive-polarity after the first potential has shifted from thenegative-polarity or the reference potential to the positive-polaritybut before the first potential shifts to the reference potential or thenegative-polarity, and the third potential shifts from thenegative-polarity or the reference potential to the positive-polarityafter the second potential has shifted from the negative-polarity or thereference potential to the positive-polarity but before the secondpotential shifts to the reference potential or the negative-polarity.

According to the liquid crystal device according to this aspect of theinvention, AC signals whose phases are shifted are applied to the firstelectrode, the second electrode, and the third electrode, in that order,in an amount of time corresponding to a single cycle in which the firstpotential shifts from the reference potential, to the positive-polarity,and to the negative-polarity. Accordingly, the direction of anelectrical field (electric flux line) produced between the electrodesmoves from the first electrode, which is closest to the display region,toward the second electrode, and then from the second electrode towardthe third electrode, as time passes. Due to the electrical fielddirection shifting, ionic impurities are first pulled to the firstelectrode, and are then pulled to the second electrode and the thirdelectrode. In other words, a liquid crystal device capable ofeffectively sweeping ionic impurities within the liquid crystal layeraway from the display region can be provided.

It is preferable that the liquid crystal device in the above examplefurther include a delay circuit into which is inputted a first AC signalserving as the AC signal and from which are outputted a second AC signalwhose phase is shifted relative to the phase of the first AC signal anda third AC signal whose phase is shifted relative to the phases of thefirst AC signal and the second AC signal.

According to this configuration, it is only necessary to input the firstAC signal into the delay circuit rather than inputting all of the firstAC signal, the second AC signal, and the third AC signal whose phasesare different from each other from the exterior, which prevents theconfiguration of an external driving circuit from becoming complicated.

It is preferable that, in the liquid crystal device in the aboveexample, the first electrode, the second electrode, and the thirdelectrode be provided in the first substrate so as to surround thedisplay region.

According to this configuration, the ionic impurities can be swept awayfrom the display region to the outside regardless of the localizationtendencies of the ionic impurities in the display region.

It is preferable that, in the liquid crystal device in the aboveexample, the display region include an electricity parting portionhaving a plurality of dummy pixel electrodes provided so as to surrounda plurality of the pixel electrodes, and that a gap between theelectricity parting portion and the first electrode be greater than agap between the first electrode and the second electrode.

According to this configuration, the influence of a horizontalelectrical field produced between the first electrode and theelectricity parting portion for sweeping away the ionic impurities canbe reduced.

It is preferable that, in the liquid crystal device in the aboveexample, the opposing electrode be provided in the second substrate, andwhen viewed from above, an outer edge of the opposing electrode belocated between the first electrode and the display region.

According to this configuration, the opposing electrode does not opposethe first electrode, the second electrode, and the third electrode withthe liquid crystal layer interposed therebetween, and thus it isdifficult for an electrical field to be produced between the opposingelectrode and the first electrode, the second electrode, and the thirdelectrode, respectively. In other words, the ionic impurities can beeffectively swept from the display region to the outside by theelectrical fields produced between the adjacent electrodes among thefirst electrode, the second electrode, and the third electrode.

It is preferable that, in the liquid crystal device in the aboveexample, the first electrode, the second electrode, and the thirdelectrode be provided in the first substrate, and the opposing electrodebe provided in the second substrate in a region that, when viewed fromabove, contains the display region and extends to a region that opposesthe first electrode, the second electrode, and the third electrode, withthe reference potential being applied to the opposing electrode.

According to this configuration, it is not necessary to performpatterning on the opposing electrode so that the opposing electrode doesnot oppose the first electrode, the second electrode, and the thirdelectrode, which makes it possible to simplify configurations such asinterconnects and the like connected to the opposing electrode.

It is preferable that, in the liquid crystal device in the aboveexample, the pixel electrode, the opposing electrode, the firstelectrode, the second electrode, and the third electrode be each coveredby an inorganic orientation layer.

According to this configuration, a liquid crystal device in which theinfluence of ionic impurities on the display is suppressed can beprovided even if an inorganic orientation layer, to which ionicimpurities adhere with ease, is employed.

It is preferable that, in the liquid crystal device in the aboveexample, the pixel electrode be formed of a conductive film having alight-reflecting property, the opposing electrode be formed of aconductive film having a light-transmissive property, and an inorganicinsulating film be formed between the pixel electrode and the inorganicorientation layer.

According to this configuration, unlike a case where DC signals areapplied to the first electrode, the second electrode, and the thirdelectrode, respectively, the potential of the AC signals will not dropeven if an inorganic insulating film is formed between the pixelelectrode and the inorganic orientation layer, and thus a reflectiveliquid crystal device capable of sweeping away ionic impurities outsideof the display region can be provided. In addition, because theinorganic insulating film is formed between the pixel electrode and theinorganic orientation layer, variations in the reference potentialcaused by work functions differing between the pixel electrode and theopposing electrode can be suppressed. In other words, a reflectiveliquid crystal device having superior display quality can be provided.

Third Application Example

An electronic device according to another aspect of the inventionincludes a liquid crystal device driven using the driving method for aliquid crystal device according to the above aspects.

Fourth Application Example

An electronic device according to another aspect of the inventionincludes the liquid crystal device according to the above aspects.

According to these aspects of the invention, an electronic device thatameliorates display problems caused by ionic impurities and has superiordisplay quality can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanyingdrawings, wherein like numbers reference like elements.

FIG. 1A is a plan view illustrating the overall configuration of aliquid crystal device according to a first embodiment, and FIG. 1B is anoverall cross-sectional view taken along a IB-IB line indicated in FIG.1A.

FIG. 2 is an equivalent circuit diagram illustrating the electricalconfiguration of the liquid crystal device according to the firstembodiment.

FIG. 3 is a cross-sectional view illustrating the overall structure of apixel in the liquid crystal device according to the first embodiment.

FIG. 4 is a plan view illustrating an overview of a relationship betweenan angled deposition direction of an inorganic material and displayproblems caused by ionic impurities.

FIG. 5A is a plan view illustrating an overview of an arrangement ofactive display pixels and dummy pixels, and FIG. 5B is a wiring diagramillustrating an electricity parting portion and an ion trappingmechanism.

FIG. 6 is a cross-sectional view, taken along a VI-VI line in FIG. 5A,illustrating an overview of the structure of a liquid crystal panel.

FIG. 7 is a timing chart illustrating square wave AC signals, serving asexamples of AC signals supplied to a first electrode, a secondelectrode, and a third electrode of an ion trapping mechanism.

FIG. 8 is a timing chart illustrating square wave AC signals, serving asexamples of AC signals supplied to a first electrode, a secondelectrode, and a third electrode of an ion trapping mechanism.

FIG. 9 is a timing chart illustrating sine wave AC signals, serving asexamples of AC signals supplied to a first electrode, a secondelectrode, and a third electrode of an ion trapping mechanism.

FIG. 10 is a graph illustrating a relationship between a degree ofmovement of ionic impurities and a temperature in a liquid crystallayer.

FIG. 11 is a circuit diagram illustrating the configuration of a delaycircuit.

FIG. 12 is a cross-sectional view illustrating the overall structure ofa liquid crystal device according to a second embodiment.

FIG. 13 is a cross-sectional view illustrating the overall structure ofa liquid crystal device according to a third embodiment.

FIG. 14 is a schematic diagram illustrating the configuration of aprojection-type display apparatus according to a fourth embodiment.

FIG. 15 is a schematic diagram illustrating the configuration of aprojection-type display apparatus according to a fifth embodiment.

FIG. 16 is a cross-sectional view illustrating the overall structure ofa liquid crystal device according to a first variation.

FIG. 17 is a cross-sectional view illustrating the overall structure ofa liquid crystal device according to a second variation.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, specific embodiments of the invention will be describedbased on the drawings. Note that the drawings used here illustrate theareas being described in an enlarged or reduced manner so that thoseareas can be recognized properly.

Note also that in the following embodiments, the phrase “on asubstrate”, for example, can refer to a constituent element beingdisposed directly on top of the substrate, a constituent element beingdisposed on top of the substrate with another constituent elementprovided therebetween, or part of the constituent element being disposeddirectly on top of the substrate while another part is disposed on topof the substrate with another constituent element provided therebetween.

First Embodiment

This embodiment describes an active matrix-type liquid crystal devicethat includes thin-film transistors (TFTs) as pixel switching elementsas an example. This liquid crystal device can be used favorably as anoptical modulation unit (a liquid crystal light valve) in aprojection-type display apparatus (a liquid crystal projector), forexample, which will be described later.

Liquid Crystal Device

First, a liquid crystal device according to this embodiment will bedescribed with reference to FIGS. 1A to 2. FIG. 1A is a general planview illustrating the configuration of the liquid crystal deviceaccording to the first embodiment, and FIG. 1B is an overallcross-sectional view taken along a IB-IB line indicated in FIG. 1A. FIG.2 is an equivalent circuit diagram illustrating the electricalconfiguration of the liquid crystal device according to the firstembodiment.

As shown in FIGS. 1A and 1B, a liquid crystal device 100 according tothis embodiment includes an element substrate 10 and an opposingsubstrate 20 that are disposed facing each other, and a liquid crystallayer 50 interposed between the stated two substrates. A substrate 10 sof the element substrate 10 and a substrate 20 s of the opposingsubstrate 20 both use a transparent substrate, such as a silicasubstrate, a glass substrate, or the like. The element substrate 10corresponds to a first substrate according to the invention, and theopposing substrate 20 corresponds to a second substrate according to theinvention.

The element substrate 10 is larger than the opposing substrate 20, andthe substrates are affixed to each other using a sealant 40 disposedalong an outer edge of the opposing substrate 20 so that a gap ispresent between the two substrates; the liquid crystal layer 50 isconfigured by filling the gap with liquid crystals having positive ornegative dielectric anisotropy. An adhesive such as a thermosetting orultraviolet light-curable epoxy resin is employed as the sealant 40.Spacers (not shown) for maintaining the aforementioned gap between thetwo substrates are intermixed with the sealant 40.

A display region E including a plurality of pixels P arranged in amatrix is provided on an inner side of the sealant 40. A parting portion21 that surrounds the display region E is provided between the sealant40 and the display region E. The parting portion 21 is configured of,for example, a metal or a metal oxidant that blocks light. Note that inaddition to the plurality of pixels P that actively display, the displayregion E may also include dummy pixels disposed so as to surround theplurality of pixels P. Furthermore, although not shown in FIGS. 1A and1B, a light-blocking portion that separates the plurality of pixels Pfrom each other in the display region E when viewed from above (a “blackmatrix” or “BM”) is provided in the opposing substrate 20.

A terminal unit in which a plurality of external connection terminals104 are arranged is provided in the element substrate 10. A data linedriving circuit 101 is provided between a first side and the sealant 40that follow the terminal unit. An examination circuit 103 is providedbetween the sealant 40 and the display region E, following a second sidethat opposes the first side. Furthermore, scanning line driving circuits102 are provided between the sealant 40 and the display region E,following third and fourth sides, respectively, that oppose each otherand are orthogonal to the first side. A plurality of wires 105 thatconnect the two scanning line driving circuits 102 are provided betweenthe sealant 40 and the examination circuit 103 on the second side.

The wires that connect the data line driving circuit 101 and thescanning line driving circuits 102 are connected to the plurality ofexternal connection terminals 104 arranged along the first side. Thefollowing descriptions will assume that a direction following the firstside is an X direction, and a direction following the third side is a Ydirection. Note that the location of the examination circuit 103 is notlimited to that described above, and the examination circuit 103 may beprovided along an inner side of the sealant 40, between the data linedriving circuit 101 and the display region E.

As shown in FIG. 1B, a light-transmissive pixel electrode 15 and athin-film transistor (“TFT”, hereinafter) 30 serving as a switchingelement are provided for each of the pixels P, along with signal lines,in the surface of the element substrate 10 facing the liquid crystallayer 50; an orientation layer 18 is formed so as to cover theseelements. A light-blocking structure that prevents light from entering asemiconductor layer of the TFT 30 and destabilizing the switchingoperations of the TFT 30 is employed. The element substrate 10 includesthe substrate 10 s as well as the pixel electrodes 15, the TFTs 30, thesignal lines, and the orientation layer 18 formed upon the substrate 10s.

The opposing substrate 20 disposed facing the element substrate 10includes the substrate 20 s, the parting portion 21 that is formed uponthe substrate 20 s, a planarizing layer 22 deposed so as to cover theparting portion 21, a common electrode 23 provided across the displayregion E and covering the planarizing layer 22, and an orientation layer24 that covers the common electrode 23. The common electrode 23corresponds to an opposing electrode according to the invention.

As shown in FIG. 1A, the parting portion 21 is provided so as tosurround the display region E, in a location that overlaps with thescanning line driving circuits 102 and the examination circuit 103 whenviewed from above. As a result, the parting portion 21 blocks light frombeing incident on the stated circuits from the opposing substrate 20 andprevents the stated circuits from operating erroneously due to suchlight. The parting portion 21 furthermore ensures high contrast in thedisplay of the display region E by blocking unnecessary stray light fromentering the display region E.

The planarizing layer 22 is configured of an inorganic material such assilicon oxide, is light-transmissive, and is provided so as to cover theparting portion 21. A method that employs plasma CVD can be given as anexample of a method for forming the planarizing layer 22.

The common electrode 23 is configured of a transparent conductive filmsuch as ITO (indium tin oxide), covers the planarizing layer 22, and iselectrically connected to upper and lower conductive portions 106provided at each of the lower corners of the opposing substrate 20, asshown in FIG. 1A. The upper and lower conductive portions 106 areelectrically connected to interconnects on the element substrate 10side.

The orientation layer 18 that covers the pixel electrodes 15 and theorientation layer 24 that covers the common electrode 23 are selectedbased on the optical design of the liquid crystal device 100. Examplesof the orientation layers 18 and 24 include an organic orientation layerproduced by forming a film from an organic material such as a polyimideand rubbing the surface thereof to achieve an approximately horizontalorientation process on liquid crystal molecules having positivedielectric anisotropy, and an inorganic orientation layer produced byforming a film from an inorganic material such as SiOx (silicon oxide)through chemical vapor deposition and achieving approximately verticalorientation for liquid crystal molecules having negative dielectricanisotropy.

The liquid crystal device 100 is transmissive, and employs an opticaldesign having a “normally-white mode”, in which the transmissibility ofthe pixels P is maximum when no voltage is being applied thereto, a“normally-black mode”, in which the transmissibility of the pixels P isminimum when no voltage is being applied thereto, or the like.Furthermore, depending on the optical design, polarizing elements aredisposed on a light-entry side and a light-exit side of a liquid crystalpanel 110 that includes the element substrate 10 and the opposingsubstrate 20.

Hereinafter, this embodiment will describe an example in which theaforementioned inorganic orientation layer is used for the orientationlayers 18 and 24, liquid crystals having negative dielectric anisotropyare used, and a normally-black mode optical design is applied.

Next, the electrical configuration of the liquid crystal device 100 willbe described with reference to FIG. 2. The liquid crystal device 100includes, in at least the display region E, a plurality of scanninglines 3 a and a plurality of data lines 6 a, serving as signal linesthat are insulated from each other and that are orthogonal to eachother, as well as capacitance lines 3 b disposed parallel to the datalines 6 a. The scanning lines 3 a extend in the X direction, whereas thedata lines 6 a extend in the Y direction.

The pixel electrodes 15, the TFTs 30, and storage capacitances 16 areprovided at the scanning lines 3 a, the data lines 6 a, and thecapacitance lines 3 b and in each region defined by the signal lines,and configure the pixel circuits of the corresponding pixels P.

Each scanning line 3 a is electrically connected to the gate of acorresponding TFT 30, and each data line 6 a is electrically connectedto the source of the corresponding TFT 30. Each pixel electrode 15 iselectrically connected to the drain of the corresponding TFT 30.

The data lines 6 a are connected to the data line driving circuit 101(see FIG. 1A), and image signals D1, D2, . . . , Dn supplied from thedata line driving circuit 101 are in turn supplied to the pixels P. Thescanning lines 3 a are connected to the scanning line driving circuits102 (see FIG. 1A), and scanning signals SC1, SC2, . . . , SCm suppliedfrom the scanning line driving circuits 102 are in turn supplied to thepixels P.

The image signals D1 to Dn supplied to the data lines 6 a from the dataline driving circuit 101 may be supplied line-sequentially in thatorder, or may be supplied in groups of a plurality of the data lines 6 athat are adjacent to each other. The scanning line driving circuits 102supply the scanning signals SC1 to SCm to the scanning lines 3 a inpulses at a predetermined timing, in a line-sequential manner.

The liquid crystal device 100 is configured so that the TFTs 30 servingas switching elements turn on for a set period when the scanning signalsSC1 to SCm are inputted thereto and the image signals D1 to Dn suppliedfrom the data lines 6 a are written into the pixel electrodes 15 at apredetermined timing as a result. The image signals D1 to Dn that havebeen written to the liquid crystal layer 50 at predetermined levels viathe pixel electrodes 15 are then held for a set period between the pixelelectrodes 15 and the common electrode 23 disposed facing the pixelelectrodes 15 on another side of the liquid crystal layer 50. Thefrequency of the image signals D1 to Dn is 60 Hz, for example.

To prevent the held image signals D1 to Dn from leaking, the storagecapacitances 16 are connected in series to liquid crystal capacitorsformed between the pixel electrodes 15 and the common electrode 23. Eachstorage capacitance 16 is provided between the drain of thecorresponding TFT 30 and the capacitance line 3 b.

Although FIG. 1A depicts a configuration in which the data lines 6 a areconnected to the examination circuit 103 and operational defects and thelike can be confirmed in the liquid crystal device 100 by detecting theimage signals during the process of manufacturing the liquid crystaldevice 100, the examination circuit 103 is not shown in the equivalentcircuit illustrated in FIG. 2.

In this embodiment, the peripheral circuits that control the driving ofthe pixel circuits include the data line driving circuit 101, thescanning line driving circuits 102, and the examination circuit 103. Theperipheral circuits may also include a sampling circuit that samples theimage signals and supplies samples to the data lines 6 a and a prechargecircuit that supplies precharge signals at predetermined voltage levelsto the data lines 6 a prior to the image signals.

Next, the structure of the pixels P in the liquid crystal device 100(the liquid crystal panel 110) according to this embodiment will bedescribed. FIG. 3 is a cross-sectional view illustrating the overallstructure of a pixel in the liquid crystal device according to the firstembodiment.

As shown in FIG. 3, first, the scanning line 3 a is formed on thesubstrate 10 s of the element substrate 10. The scanning line 3 a isconfigured of a metal element including at least one of Al (aluminum),Ti (titanium), Cr (chromium), W (tungsten), Ta (tantalum), Mo(molybdenum), and the like, an alloy, a metal silicide, a polysilicide,a nitride, or a layered combination thereof, and has light-blockingproperties.

A first insulating film (a base insulating film) 11 a configured ofsilicon oxide, for example, is formed so as to cover the scanning line 3a, and a semiconductor layer 30 a is formed in an island shape on thefirst insulating film 11 a. The semiconductor layer 30 a is configuredof a polycrystal silicon film, for example, into which ion impuritiesare injected, forming an LDD (lightly-doped drain) structure including afirst source-drain region, a junction region, a channel region, ajunction region, and a second source-drain region.

A second insulating film (gate insulator) 11 b is formed so as to coverthe semiconductor layer 30 a. A gate electrode 30 g is formed in aposition that faces the channel region, with the second insulating film11 b located therebetween.

A third insulating film 11 c is formed so as to cover the gate electrode30 g and the second insulating film 11 b, and two contact holes CNT1 andCNT2 that pass through the second insulating film 11 b and the thirdinsulating film 11 c are formed in positions corresponding to therespective end areas of the semiconductor layer 30 a.

A source electrode 31 connected to the first source-drain region via thecontact hole CNT1 is formed along with the data line 6 a by forming aconductive film of a light-blocking conductive material such as Al(aluminum), an alloy thereof, or the like so as to coat the two contactholes CNT1 and CNT2 and cover the third insulating film 11 c andpatterning the conductive film. A drain electrode 32 (a first relayelectrode 6 b) connected to the second source-drain region via thecontact hole CNT2 is formed at the same time.

Next, a first interlayer insulating film 12 is formed so as to cover thedata line 6 a as well as the first relay electrode 6 b and the thirdinsulating film 11 c. The first interlayer insulating film 12 isconfigured of silicon oxide, nitride, or the like, for example. Aplanarizing process for planarizing non-planarities produced in thesurface of the first interlayer insulating film 12 when the region inwhich the TFT 30 is provided is covered is carried out thereon. Chemicalmechanical polishing (CMP), spin coating, and so on can be given asexamples of techniques used for the planarizing process.

A contact hole CNT3 that passes through the first interlayer insulatingfilm 12 is formed in a position corresponding to the first relayelectrode 6 b. An interconnect 7 a and a second relay electrode 7 belectrically connected to the first relay electrode 6 b via the contacthole CNT3 are formed by forming a conductive film of a light-blockingmetal such as Al (aluminum), an alloy thereof, or the like so as to coatthe contact hole CNT3 and cover the first interlayer insulating film 12and patterning the conductive film.

The interconnect 7 a is formed so as to overlap with the semiconductorlayer 30 a of the TFT 30, the data line 6 a, and so on when viewed fromabove; a fixed potential is applied to the interconnect 7 a, and thusthe interconnect 7 a functions as a shield layer.

A second interlayer insulating film 13 a is formed so as to cover theinterconnect 7 a and the second relay electrode 7 b. The secondinterlayer insulating film 13 a can also be formed of silicon oxide,nitride, or the like, or an oxynitride, and a planarizing process suchas CMP is carried out thereon.

A contact hole CNT4 is formed in the second interlayer insulating film13 a in a position corresponding to the second relay electrode 7 b. Afirst capacitance electrode 16 a and a third relay electrode 16 d areformed by forming a conductive film of a light-blocking metal such as Al(aluminum), an alloy thereof, or the like so as to coat the contact holeCNT4 and cover the second interlayer insulating film 13 a and patterningthe conductive film.

An insulating film 13 b is formed through patterning so as to cover anouter edge of the first capacitance electrode 16 a in an area thereofthat faces a second capacitance electrode 16 c on another side of adielectric layer 16 b, which are formed later. In addition, theinsulating film 13 b is formed through patterning so as to cover outeredges of the third relay electrode 16 d in areas aside from an area thatoverlaps with a contact hole CNT5.

The dielectric layer 16 b is formed covering the insulating film 13 band the first capacitance electrode 16 a. A silicon nitride film, asingle-layer film such as hafnium oxide (HfO₂), alumina (Al₂O₃),tantalum oxide (Ta₂O₅), or the like, or a multilayer film in which atleast two types of such single-layer films are stacked may be used asthe dielectric layer 16 b. The dielectric layer 16 b is removed throughetching or the like in an area thereof that overlaps with the thirdrelay electrode 16 d when viewed from above. The second capacitanceelectrode 16 c is formed facing the first capacitance electrode 16 a andconnected to the third relay electrode 16 d by forming a conductive filmof TiN (titanium nitride), for example, so as to cover the dielectriclayer 16 b and patterning the conductive film. The storage capacitance16 is configured of the dielectric layer 16 b, the first capacitanceelectrode 16 a and the second capacitance electrode 16 c that aredisposed facing each other with the dielectric layer 16 b therebetween.

Next, a third interlayer insulating film 14 is formed so as to cover thesecond capacitance electrode 16 c and the dielectric layer 16 b. Thethird interlayer insulating film 14 can also be formed of silicon oxide,nitride, or the like, and a planarizing process such as CMP is carriedout thereon. The contact hole CNT5 is formed passing through the thirdinterlayer insulating film 14 so that the second capacitance electrode16 c makes contact with the third relay electrode 16 d.

A transparent conductive film (electrode film) configured of ITO, forexample, is deposed so as to coat the contact hole CNT5 and cover thethird interlayer insulating film 14. The pixel electrode 15 that iselectrically connected to the second capacitance electrode 16 c and thethird relay electrode 16 d via the contact hole CNT5 is formed bypatterning this transparent conductive film (electrode film).

The second capacitance electrode 16 c is electrically connected to thedrain electrode 32 of the TFT 30 via the third relay electrode 16 d, thecontact hole CNT4, the second relay electrode 7 b, the contact holeCNT3, and the first relay electrode 6 b, and is electrically connectedto the pixel electrode 15 via the contact hole CNT5.

The first capacitance electrode 16 a is formed so as to span across aplurality of the pixels P, and functions as the capacitance line 3 b inthe equivalent circuit (see FIG. 2). A fixed potential is applied to thefirst capacitance electrode 16 a. Through this, a potential applied tothe pixel electrode 15 via the drain electrode 32 of the TFT 30 can beheld between the first capacitance electrode 16 a and the secondcapacitance electrode 16 c.

A plurality of wires are formed on the substrate 10 s of the elementsubstrate 10, and a wire layer is indicated by the reference numerals ofinsulating films, interlayer insulating films, and so on that provideinsulation between the wires. In other words, the first insulating film11 a, the second insulating film 11 b, and the third insulating film 11c are collectively referred to as a wire layer 11. The representativewire in the wire layer 11 is the scanning line 3 a. The representativewire in a wire layer 12 is the data line 6 a. The second interlayerinsulating film 13 a, the insulating film 13 b, and the dielectric layer16 b are collectively referred to as a wire layer 13, and therepresentative wire in the wire layer 13 is the interconnect 7 a.Likewise, the representative wire in a wire layer 14 is the firstcapacitance electrode 16 a (the capacitance line 3 b).

The orientation layer 18 is formed so as to cover the pixel electrode15, and the orientation layer 24 is formed so as to cover the commonelectrode 23 in the opposing substrate 20 disposed facing the elementsubstrate 10 on another side of the liquid crystal layer 50. Asdescribed earlier, the orientation layers 18 and 24 are inorganicorientation layers, and are collections of columns 18 a and 24 a,respectively, in which an inorganic material such as silicon oxide isdeposed in column form at an angle from a predetermined direction, forexample. Liquid crystal molecules LC having negative dielectricanisotropy relative to the orientation layers 18 and 24 are alignedsubstantially vertically (vertical alignment, or VA) at a pretilt angleθp of 3 to 5 degrees in the angled direction of the columns 18 a and 24a relative to the normal direction of the orientation layer surfaces.When the liquid crystal layer 50 is driven by applying an AC voltage (adriving signal) between the pixel electrode 15 and the common electrode23, the liquid crystal molecules LC behave (vibrate) so as to sway inthe direction of an electrical field produced between the pixelelectrode 15 and the common electrode 23.

FIG. 4 is a plan view illustrating an overview of a relationship betweenan angled deposition direction of an inorganic material and displayproblems caused by ionic impurities. As shown in FIG. 4, the angleddeposition direction of the inorganic material where the columns 18 aand 24 a are formed is, for example in the element substrate 10, adirection that intersects with the Y direction from the upper-right tothe lower-left at a predetermined angle of direction θa, as indicated bya broken line arrow. In the opposing substrate 20 that faces the elementsubstrate 10, the angled deposition direction is a direction thatintersects with the Y direction from the lower-left to the upper-rightat the predetermined angle of direction θa, as indicated by a solid linearrow. The predetermined angle θa is 45 degrees, for example. Note thatthe angled deposition direction shown in FIG. 4 is a direction foundwhen viewing the liquid crystal device 100 from the side on which theopposing substrate 20 is disposed.

When the liquid crystal layer 50 is driven and the liquid crystalmolecules LC behave (vibrate) as a result, the liquid crystal moleculesLC flow, in the angled deposition direction indicated by the broken orsolid line arrows shown in FIG. 4, near the borders between the liquidcrystal layer 50 and the orientation layers 18 and 24. If the liquidcrystal layer 50 contains positive or negative-polarity ionicimpurities, the ionic impurities will move toward the corners of thedisplay region E along with the flow of the liquid crystal molecules LC,becoming possibly localized in the corners. The localization of theionic impurities leads to a drop in the insulation resistance of theliquid crystal layer 50 in the pixels P located in the corners, which inturn leads to a drop in the driving potential of those pixels P; as aresult, display unevenness, burn-in due to electrification, and so onwill become prominent, as indicated in FIG. 4. Inorganic orientationlayers are particularly susceptible to attracting ionic impurities, andthus such display unevenness, burn-in, and so on will be more prominentwhen inorganic orientation layers are used for the orientation layers 18and 24 as opposed to organic orientation layers.

In the liquid crystal device 100 according to this embodiment, an iontrapping mechanism that sweeps ionic impurities off from the displayregion E is provided between the sealant 40 and the display region E isorder to ameliorate display unevenness, burn-in, and so on as indicatedin FIG. 4. The ion trapping mechanism according to this embodiment willbe described hereinafter with reference to FIGS. 5A to 6.

FIG. 5A is a plan view illustrating an overview of an arrangement ofactive display pixels and dummy pixels; FIG. 5B is a wiring diagramillustrating an electricity parting portion and the ion trappingmechanism; and FIG. 6 is a cross-sectional view, taken along a VI-VIline in FIG. 5A, illustrating an overview of the structure of the liquidcrystal panel.

As shown in FIG. 5A, the display region E in the liquid crystal device100 according to this embodiment includes an active display region E1 inwhich the active display pixels P are disposed and a dummy pixel regionE2 that surrounds the active display region E1 and in which a pluralityof dummy pixels DP are disposed. The parting portion 21, which haslight-blocking properties as described earlier, is provided between theframe-shaped region in which the sealant 40 is disposed and the dummypixel region E2, and the region in which the parting portion 21 isdisposed corresponds to a parting region E3 that operates regardless ofwhether the liquid crystal device 100 is on or off.

Sets of two dummy pixels DP are disposed in the dummy pixel region E2 onboth sides of the active display region E1 in both the X direction andthe Y direction. Note that the number of dummy pixels DP disposed in thedummy pixel region E2 is not limited thereto, and any number may be usedas long as there is at least one dummy pixel DP on both sides of theactive display region E1 in both the X direction and the Y direction.There may be three or more dummy pixels DP, and the number of dummypixels DP may differ between the X direction and the Y direction. Inthis embodiment, the dummy pixels DP function as the electricity partingportion, and thus reference numeral 120 will be given to the pluralityof dummy pixels DP and the dummy pixels DP will be referred to as anelectricity parting portion 120.

As shown in FIG. 5B, each of a plurality of the dummy pixels DP disposedalong the edges of the active display region E1 so as to surround theactive display region E1 includes a dummy pixel electrode 122. Each of aplurality of the dummy pixels DP disposed so as to surround theplurality of the dummy pixels DP that include the dummy pixel electrodes122 includes a dummy pixel electrode 121. A plurality of the dummy pixelelectrodes 121 and a plurality of the dummy pixel electrodes 122disposed along the X direction are disposed adjacent to each other inthe Y direction, whereas the plurality of dummy pixel electrodes 121 andthe plurality of dummy pixel electrodes 122 disposed along the Ydirection are disposed adjacent to each other in the X direction. Inother words, the electricity parting portion 120 includes the pluralityof dummy pixel electrodes 121 and 122 disposed in the X direction andthe Y direction, respectively.

An ion trapping mechanism 130 according to this embodiment includes afirst electrode 131, a second electrode 132, and a third electrode 133that are each provided so as to surround the electricity parting portion120. The first electrode 131, the second electrode 132, and the thirdelectrode 133 each have quadrangular frame shapes when viewed fromabove; the first electrode 131 is disposed in a position closest to theelectricity parting portion 120, the third electrode 133 is disposed ina position farthest from the electricity parting portion 120, and thesecond electrode 132 is disposed between the first electrode 131 and thethird electrode 133.

One end of each wire in a pair of routing wires 135 extending in the Ydirection is electrically connected to both ends of a lower side,extending in the X direction, of the first electrode 131 that isquadrangular when viewed from above. The other ends of the respectiverouting wires 135 are connected to the external connection terminals 104in the element substrate 10. The external connection terminals 104 towhich the pair of routing wires 135 are connected will be distinguishedfrom the other external connection terminals 104 as external connectionterminals 104 (It1).

Likewise, one end of each wire in a pair of routing wires 136 extendingin the Y direction is electrically connected to both ends of a lowerside, extending in the X direction, of the second electrode 132 that isquadrangular when viewed from above. The other ends of the respectiverouting wires 136 are connected to the external connection terminals 104in the element substrate 10. The external connection terminals 104 towhich the pair of routing wires 136 are connected will be distinguishedfrom the other external connection terminals 104 as external connectionterminals 104 (It2).

Likewise, one end of each wire in a pair of routing wires 137 extendingin the Y direction is electrically connected to both ends of a lowerside, extending in the X direction, of the third electrode 133 that isquadrangular when viewed from above. The other ends of the respectiverouting wires 137 are connected to the external connection terminals 104in the element substrate 10. The external connection terminals 104 towhich the pair of routing wires 137 are connected will be distinguishedfrom the other external connection terminals 104 as external connectionterminals 104 (It3).

The ion trapping mechanism 130 includes the first electrode 131, thesecond electrode 132, the third electrode 133, and the routing wires135, 136, and 137 that transmit potentials supplied from the externalconnection terminals 104 (It1, It2, and It3) to the first electrode 131,the second electrode 132, and the third electrode 133, respectively.

The common electrode 23 is provided so as to include the active displayregion E1 and overlap with the plurality of the dummy pixel electrodes121 and 122 in the electricity parting portion 120 when viewed fromabove. In other words, the common electrode 23 is provided across thedisplay region E, and does not overlap with the first electrode 131, thesecond electrode 132, and the third electrode 133 of the ion trappingmechanism 130 when viewed from above.

The upper and lower conductive portions 106 are provided on both endsides of the plurality of external connection terminals 104. The upperand lower conductive portions 106 and the external connection terminals104 on both end sides are electrically connected to each other viarouting wires 107. Meanwhile, lead wires 23 a that are connected to theupper and lower conductive portions 106 are provided in the commonelectrode 23. A common potential (LCCOM) is applied to the externalconnection terminals 104 on both end sides. Accordingly, the externalconnection terminals 104 electrically connected to the common electrode23 are referred to as external connection terminals 104 (LCCOM). Inother words, the common potential (LCCOM) is applied to the commonelectrode 23.

Although this embodiment employs a configuration in which potentials aresupplied from two each of the external connection terminals 104 (It1,It2, and It3) in order to suppress the potentials supplied to the firstelectrode 131, the second electrode 132, and the third electrode 133from varying based on the positions of the first electrode 131, thesecond electrode 132, and the third electrode 133 on the elementsubstrate 10, it should be noted that the configuration is not limitedthereto. One, or three or more, external connection terminals 104 (It1,It2, and It3) may be employed instead.

Furthermore, the first electrode 131 is not limited to anelectrically-closed quadrangular electrode when viewed from above. Therouting wires 135 may be connected to one end thereof, whereas the otherend thereof may be in an open state. The same applies to the secondelectrode 132 and the third electrode 133, where the routing wires maybe connected to one end thereof, whereas the other end thereof may be inan open state, respectively.

In this embodiment, ionic impurities that are localized at the cornersof the display region E, as indicated in FIG. 4, are swept to theoutside of the display region E by the ion trapping mechanism 130. Assuch, the common electrode 23 is disposed so as not to overlap with theion trapping mechanism 130, which will be described in detail later.Accordingly, it is preferable for the positions where the lead wires 23a of the common electrode 23 overlap with the first electrode 131, thesecond electrode 132, and the third electrode 133 when viewed fromabove, or in other words, the leading positions of the lead wires 23 ain the common electrode 23, to avoid overlapping with the corners of thefirst electrode 131, the second electrode 132, and the third electrode133.

As shown in FIG. 6, the element substrate 10 of the liquid crystaldevice 100 includes a plurality of the wire layers 11 to 14 on thesubstrate 10 s. The pixel electrodes 15 of the pixels P, the dummy pixelelectrodes 121 and 122 in the dummy pixels DP (the electricity partingportion 120), and the first electrode 131, the second electrode 132, andthe third electrode 133 of the ion trapping mechanism 130 are eachformed on the third interlayer insulating film 14. The dummy pixelelectrodes 121 and 122, the first electrode 131, the second electrode132, and the third electrode 133 are formed using the same transparentconductive film as the pixel electrodes 15 (an ITO film, for example)when forming the pixel electrodes 15. When viewed from above, the shapeand size of the dummy pixel electrodes 121 and 122, the pitch at whichthe dummy pixel electrodes 121 and 122 are disposed, and so on are thesame as for the pixel electrodes 15.

The first electrode 131, the second electrode 132, and the thirdelectrode 133 are disposed at equal intervals in the X direction.Although not shown in FIG. 6, it should be noted that the firstelectrode 131, the second electrode 132, and the third electrode 133 aredisposed at equal intervals in the Y direction as well. The firstelectrode 131, the second electrode 132, and the third electrode 133 areconnected to interconnects provided in a lower wire layer, which lead tothe external connection terminals 104 (It1, It2, and It3), respectively.The electrode portions of the first electrode 131, the second electrode132, and the third electrode 133 are 4 μm wide, for example, and thepitch at which the first electrode 131, the second electrode 132, andthe third electrode 133 are disposed is 8 μm, for example. In otherwords, an interval between the first electrode 131 and the secondelectrode 132 and an interval between the second electrode 132 and thethird electrode 133 are 4 μm.

Meanwhile, an interval between the first electrode 131 and the dummypixel electrodes 121 adjacent thereto in the X direction is greater thanan interval between the first electrode 131 and the second electrode 132in the X direction. Although not shown in FIG. 6, an interval betweenthe first electrode 131 and the dummy pixel electrodes 121 adjacentthereto in the Y direction is greater than an interval between the firstelectrode 131 and the second electrode 132 in the Y direction as well.The intervals between the first electrode 131 and the dummy pixelelectrodes 121 in the X direction and the Y direction is no less than 10μm, for example.

Each of the dummy pixel electrodes 121 and 122 is electrically connectedto the corresponding TFT 30 provided in a lower layer. In the case wherethe liquid crystal device 100 is in a normally-black mode, an ACpotential at, for example, a magnitude that does not change thetransmissibility of the dummy pixels DP is applied to the plurality ofdummy pixel electrodes 121 and 122 via the corresponding TFTs 30 so thatthe electricity parting portion 120 is continuously in a “black mode(black display)” regardless of the display state of the pixels P in theactive display region E1.

As described with reference to FIGS. 3 and 4, when the liquid crystaldevice 100 is being driven (that is, during a display period),positive-polarity (+) or negative-polarity (−) ionic impurities movefrom the corners of the active display region E1 to the dummy pixelregion E2 with a flow produced by the behavior of the liquid crystalmolecules LC.

Meanwhile, AC signals are supplied to the first electrode 131, thesecond electrode 132, and the third electrode 133 of the ion trappingmechanism 130 so that a direction of an electrical field (electric fluxline) produced between adjacent electrodes aligns with a direction fromthe first electrode 131, which is closer to the electricity partingportion 120 (or the display region E), toward the third electrode 133.The AC signals are signals that shift between a high potential and a lowpotential, with the common potential (LCCOM) supplied to the commonelectrode 23 serving as a reference potential. The positive-polarity (+)or negative-polarity (−) ionic impurities are swept from the dummy pixelregion E2 to the parting region E3 by the movement of the statedelectrical field direction from the first electrode 131 to the thirdelectrode 133.

In the opposing substrate 20 according to this embodiment, the commonelectrode 23 is not provided in areas opposing the first electrode 131,the second electrode 132, and the third electrode 133 on another side ofthe liquid crystal layer 50. Accordingly, it is difficult for anelectrical field to arise between the common electrode 23 and the firstelectrode 131, the second electrode 132, and the third electrode 133,respectively. In other words, the ionic impurities are swept into theparting region E3 without the movement of the ionic impurities beinginhibited by an electrical field produced between the common electrode23 and the first electrode 131, the second electrode 132, and the thirdelectrode 133, respectively.

Driving Method of Liquid Crystal Device 100

Next, a driving method for the liquid crystal device 100 will bedescribed with reference to FIGS. 7 and 8, using examples in whichspecific AC signals are applied to the first electrode 131, the secondelectrode 132, and the third electrode 133, respectively, via thecorresponding external connection terminals 104 (It1, It2, It3). FIGS. 7and 8 are timing charts indicating examples of the AC signals suppliedto the first electrode, the second electrode, and the third electrode ofthe ion trapping mechanism, respectively. FIGS. 7 and 8 indicateexamples of square wave AC signals.

In the driving method for the liquid crystal device 100 according tothis embodiment, for example, square wave AC signals are applied to thefirst electrode 131, the second electrode 132, and the third electrode133, respectively, as shown in FIG. 7. Specifically, AC signals havingthe same frequency are applied to the first electrode 131, the secondelectrode 132, and the third electrode 133 so that after a firstpotential of the first electrode 131 shifts from the positive-polarity(+) or the reference potential to the negative-polarity (−) but beforethe first potential shifts to the reference potential or thepositive-polarity (+), a second potential of the second electrode 132shifts from the positive-polarity (+) or the reference potential to thenegative-polarity (−), and after the second potential shifts to thenegative-polarity (−) but before the second potential shifts to thereference potential or the positive-polarity (+), a third potential ofthe third electrode 133 shifts from the positive-polarity (+) or thereference potential to the negative-polarity (−); and so that after thefirst potential of the first electrode 131 shifts from anegative-polarity (−) or the reference potential to thepositive-polarity (+) but before the first potential shifts to thereference potential or the negative-polarity (−), the second potentialof the second electrode 132 shifts from the negative-polarity (−) or thereference potential to the positive-polarity (+), and after the secondpotential shifts from the negative-polarity (−) or the referencepotential to the positive-polarity (+) but before the second potentialshifts to the reference potential or the negative-polarity (−), thethird potential of the third electrode 133 shifts from thenegative-polarity (−) or the reference potential to thepositive-polarity (+).

The AC signal supplied to the second electrode 132 is delayed along atime axis t by a time Δt relative to the AC signal supplied to the firstelectrode 131. Likewise, the AC signal supplied to the third electrode133 is delayed along the time axis t by a time Δt relative to the ACsignal supplied to the second electrode 132. For example, if the time Δtis ⅓ of a cycle, the phases of the AC signals supplied to the firstelectrode 131, the second electrode 132, and the third electrode 133,respectively, are shifted from each other by ⅓ of a cycle. To rephrase,a maximum phase shift amount Δt when the phases of the potentials of thefirst electrode 131, the second electrode 132, and the third electrode133 are shifted from each other is a value obtained by dividing a singlecycle of the AC signal by a number of electrodes n.

Although the square wave AC signals shown in FIG. 7 shift between a highpotential (5 V) and a low potential (−5 V) with 0 V serving as thereference potential, the reference potential, high potential, and lowpotential settings are not limited thereto.

From a time t₀ to a time t₁ in the timing chart shown in FIG. 7, whenthe first potential of the first electrode 131 is positive-polarity (+)at 5 V, the second potential of the second electrode 132 that isadjacent to the first electrode 131 is negative-polarity (−) at −5 V.Accordingly, as indicated in FIG. 6, an electrical field oriented fromthe first electrode 131 toward the second electrode 132 (the electricflux line indicated by the solid line) is produced between the firstelectrode 131 and the second electrode 132.

Meanwhile, from the time t₁ to a time t₂, when the second potential ofthe second electrode 132 is positive-polarity (+) at 5 V, the thirdpotential of the third electrode 133 that is adjacent to the secondelectrode 132 is negative-polarity (−) at −5 V. Accordingly, asindicated in FIG. 6, an electrical field oriented from the secondelectrode 132 toward the third electrode 133 is produced between thesecond electrode 132 and the third electrode 133.

Furthermore, from the time t₂ to a time t₃, when the third potential ofthe third electrode 133 is positive-polarity (+) at 5 V, the secondpotential of the second electrode 132 that is adjacent to the thirdelectrode 133 shifts from positive-polarity (+) at 5 V tonegative-polarity (−) at −5 V. Accordingly, it is difficult for anelectrical field to arise between the second electrode 132 and the thirdelectrode 133 in a constant direction. In other words, in a period oftime from the time to t₀ the time t₃, which corresponds to a singlecycle of the AC signal, a distribution of the electrical field betweenthe first electrode 131, the second electrode 132, and the thirdelectrode 133 scrolls from the first electrode 131 to the thirdelectrode 133 over time. Producing an electrical field in this mannerusing AC signals will be called “electrical field scrolling”hereinafter.

Ionic impurities may include positive-polarity (+) impurities andnegative-polarity (−) impurities. Accordingly, positive-polarity (+) ornegative-polarity (−) ionic impurities can be pulled toward the firstelectrode 131 based on the polarity of the first potential at the firstelectrode 131. Allowing the ionic impurities that have been pulledtoward the first electrode 131 to remain as-is may cause ionicimpurities to continue to accumulate and influence the electricityparting portion 120, the display in the active display region E1, and soon, and thus it is preferable for the ionic impurities pulled toward thefirst electrode 131 to then be moved to the second electrode 132, thethird electrode 133, and so on.

In this embodiment, the distribution of the electrical field producedbetween the electrodes is scrolled from the first electrode 131 to thethird electrode 133 by applying the AC signals, whose phases are shiftedfrom each other, to the first electrode 131, the second electrode 132,and the third electrode 133 as described above. As a result,positive-polarity (+) or negative-polarity (−) ionic impurities pulledtoward the first electrode 131 can be moved to the third electrode 133.As such, the first electrode 131, the second electrode 132, and thethird electrode 133 may also be referred to collectively as ion trappingelectrodes 131, 132, and 133.

In order for the ionic impurities to be swept to the third electrode 133with certainty through electrical field scrolling, it is necessary toset the frequency of the AC signals in consideration of the velocity atwhich the ionic impurities move. If the velocity of the electrical fieldscrolling is higher than the velocity at which the ionic impuritiesmove, there is a risk that the ionic impurities will not keep up withthe electrical field scrolling and the effect of sweeping away the ionicimpurities will drop.

The inventors derived a preferred frequency f (Hz) of the AC signals inthe ion trapping mechanism 130 as described hereinafter.

A movement velocity v (m/s) of the ionic impurities in the liquidcrystal layer can be found by taking the product of an electrical fieldintensity e (V/m) between adjacent ion trapping electrodes and a degreeof movement μ (m²/V·s) of the ionic impurities, as represented byFormula (1).That is, v=e·μ  (1)

The electrical field intensity e (V/m) is a value obtained by dividing apotential difference Vn between adjacent ion trapping electrodes by adisposal pitch p (m) of the ion trapping electrodes, as represented byFormula (2).That is, e=Vn/p  (2)

The potential difference Vn between adjacent ion trapping electrodes isequivalent to twice an effective voltage V_(E) in the AC signals, andthus the following Formula (3) can be derived.That is, e=2V _(E) /p  (3)Note that as shown in FIG. 7, the effective voltage V_(E) of a squarewave AC signal corresponds to a potential relative to the referencepotential of the square wave, and is 5 V in this embodiment.

By substituting Formula (3) in Formula (1), the movement velocity v(m/s) of the ionic impurities is expressed as Formula (4).That is, v=2μV _(E) /p  (4)

A time td over which the ionic impurities move between adjacent iontrapping electrodes is, as indicated by Formula (5), a value obtained bydividing the disposal pitch p of the adjacent ion trapping electrodes bythe movement velocity v of the ionic impurities.That is, td=p/v=p ²/2μV _(E)  (5)

Accordingly, the preferred frequency f (Hz) is found by scrolling theelectrical field in accordance with the time td over which the ionicimpurities move between adjacent ion trapping electrodes. A electricalfield scrolling time corresponds to a phase difference Δt between the ACsignals, and thus assuming Δt is 1/n cycles as described earlier, thepreferred frequency f (Hz) can be derived through the following Formula(6). Here, n represents the number of ion trapping electrodes.That is, f=1/n/td=2μV _(E) /np ²  (6)

As described earlier, if it is assumed that the phase difference Δt ofthe AC signals applied to adjacent ion trapping electrodes is ⅓ a cycle,and the AC signals are square wave AC signals that move between 5 V and−5 V with 0 V as a reference potential, the potential difference Vnbetween adjacent ion trapping electrodes in the ion trapping mechanism130 is 10 V. Furthermore, assuming that the disposal pitch p between theion trapping electrodes in the ion trapping mechanism 130 is 8 μm andthe degree of movement μ of the ionic impurities is 2.2×10⁻¹⁰ (m²/V·s),the preferred frequency f is approximately 12 Hz, based on Formula (6).

Note that the value of the degree of movement μ of the ionic impuritiesis discussed in, for example, A. Sawada, A. Manabe, and S. Naemura, “AComparative Study on the Attributes of Ions in Nematic and IsotropicPhases”, Jpn. J. Appl. Phys. Vol. 40, p 220-p 224 (2001).

Increasing the frequency f of the AC signal beyond 12 Hz results in theionic impurities being unable to keep up with the electrical fieldscrolling, and thus it is preferable for the frequency f to be equal to12 Hz or less than 12 Hz. On the other hand, an extremely low frequencyf will result in a DC current being applied between the ion trappingelectrodes, resulting in the breakdown of liquid crystals, displayproblems such as burn-in or spotting, or the like, and is thus notpreferable. The preferred frequency f can be increased if the disposalpitch of the ion trapping electrodes 131, 132, and 133 is reduced beyond8 μm. Furthermore, to sweep the ionic impurities further away from thedisplay region E, it is preferable to provide even more than three iontrapping electrodes.

Meanwhile, when the width of each of the ion trapping electrodes 131,132, and 133 is taken as L and each gap between adjacent ion trappingelectrodes 131, 132, and 133 is taken as S, it is preferable for thewidth L to be equal to the gap S or lower than the gap S. This isbecause if the width L is greater than the gap S, the time in which theionic impurities move will be greater on ion trapping electrodes wherethe electrical field does not easily move than between ion trappingelectrodes where the electrical field moves, resulting in a risk thatthe effect of sweeping away the ionic impurities will drop.

The AC signals applied to the ion trapping electrodes 131, 132, and 133are not limited to the square wave AC signals indicated in FIG. 7. Thesquare waves illustrated in FIG. 8, for example, may be employed aswell.

In the square wave AC signals in FIG. 7, the time for which thepotential is positive-polarity (+) is equal to the time for which thepotential is negative-polarity (−); however, for example, as shown inFIG. 8, AC signals set so that a time t₅ for which the potential isnegative-polarity (−) is longer than a time t₄ for which the potentialis positive-polarity (+) may be employed instead. Depending on theprocess for manufacturing the liquid crystal device 100, the liquidcrystal layer 50 may contain both positive-polarity (+) andnegative-polarity (−) ionic impurities, and it is known thatpositive-polarity (+) ionic impurities cause a greater drop in displayquality than negative-polarity (−) ionic impurities. Accordingly,applying AC signals in which the time t₅ for which the potential isnegative-polarity (−) to each of the ion trapping electrodes 131, 132,and 133 makes it possible to effectively sweep the positive-polarity (+)ionic impurities away.

Furthermore, although the square wave AC signals may be oscillatedbetween, for example, two potential values, or 5 V and −5 V, relative toa reference potential of 0 V, as indicated in FIGS. 7 and 8, thewaveforms may instead be set to move among three or more differentpotentials. Through this, the ionic impurities can be moved smoothlyfrom the first electrode 131 to the third electrode 133 through thesecond electrode 132 in the ion trapping mechanism 130. Furthermore,triangular wave AC signals can also be employed in addition to thesquare wave AC signals indicated in FIGS. 7 and 8. Further still, the ACsignals applied to the respective ion trapping electrodes 131, 132, and133 may be sine waves having mutually different phases within a singletime cycle, as shown in FIG. 9. However, compared to an analog circuitthat generates an analog signal such as a sine wave, a digital circuitthat generates a square wave makes it easier to simplify the circuitconfiguration.

Meanwhile, as long as the AC signals have the same frequency, theamplitude of the AC signals applied to the first electrode 131, thesecond electrode 132, and the third electrode 133, or in other words,the maximum positive-polarity potentials and the maximumnegative-polarity potential relative to the reference potential, neednot necessarily be equal. For example, an AC signal that oscillatesbetween 5 V and −5 V relative to a reference potential of 0 V is appliedto the first electrode 131 as mentioned earlier. However, an AC signalthat oscillates between 7.5 V and −7.5 V relative to the referencepotential of 0 V is applied to the second electrode 132, and an ACsignal that oscillates between 10 V and −10 V relative to the referencepotential of 0 V is applied to the third electrode 133. By increasingthe amplitude of the AC signals applied to the three ion trappingelectrodes 131, 132, and 133 as the ion trapping electrodes 131, 132,and 133 progress away from the display region E in this manner makes itpossible to effectively sweep away the ionic impurities.

As described earlier, driving the pixels P results in the liquid crystalmolecules LC flowing within the liquid crystal layer 50, and the ionicimpurities move through the display region E as a result of this flow.The velocity of the flow is thought to depend on the frequency of thedriving signal that drives the pixels P. It is preferable for themovement of the electrical fields produced between the ion trappingelectrodes 131, 132, and 133 to be slower in order to pull the ionicimpurities, which move due to the stated flow, from the display region Eto the ion trapping electrodes 131, 132, and 133 with certainty. Inother words, it is preferable for the frequency f (Hz) of the AC signalsapplied to the ion trapping electrodes 131, 132, and 133 to be lowerthan the frequency of the driving signal that drives the pixels P.

On the other hand, the degree of movement μ (movement velocity v) of theionic impurities depends on the temperature. Thus if the temperaturewhen the liquid crystal device 100 is actually driven is higher than anormal temperature, an effect in which the ionic impurities are sweptaway can be achieved even if the frequency f is set to be higher than 12Hz.

FIG. 10 is a graph illustrating a relationship between the degree ofmovement μ of the ionic impurities and the temperature. Note that thegraph shown in FIG. 10 has been obtained by referring to values of thedegree of movement μ of the ionic impurities discussed in theaforementioned A. Sawada, A. Manabe, and S. Naemura, “A ComparativeStudy on the Attributes of Ions in Nematic and Isotropic Phases”, Jpn.J. Appl. Phys. Vol. 40, p 220-p 224 (2001).

As shown in FIG. 10, the value of the degree of movement μ of the ionicimpurities when the temperature is 25° C. is approximately 2.2×10⁻¹⁰(m²/V·s), and the value of log μ is −9.6. As opposed to this, the valueof the degree of movement μ of the ionic impurities when the temperatureis 60° C. is approximately 2.2×10⁻⁹ (m²/V·s), and the value of log μ is−8.7. In other words, the degree of movement μ of the ionic impuritiesat 60° C. is approximately 10 times the degree of movement μ at 25° C. Atemperature of 60° C. is focused on here in consideration of thetemperature when the liquid crystal device 100 is used as a light valvein a projection-type display apparatus, which will be described later.

If μ=2.2×10⁻⁹ (m²/V·s) when n=3, V_(E)=5 V, p=8 μm, and the temperatureis 60° C. is applied to the aforementioned Formula (6), the optimalfrequency f is approximately 113 Hz. In this state, it is thought thatan effect of sweeping away the ionic impurities can be achieved despitethe optimal frequency f of the AC signals applied to the ion trappingelectrodes 131, 132, and 133 being greater than the driving frequency of60 Hz in this embodiment. To rephrase, it is thought that if the drivingfrequency is set to a higher frequency than the optimal frequency f ofthe AC signals, such as 120 Hz, the ionic impurities can be swept awayin a more effective manner.

Next, a method (means) for applying the AC signals will be described. Inthis embodiment, AC signals having the same frequency but with mutuallyshifted phases are applied to the first electrode 131, the secondelectrode 132, and the third electrode 133, respectively, of the iontrapping mechanism 130 from the exterior via the three externalconnection terminals 104 (It1, It2, and It3), as indicated in FIG. 5B;however, the method (means) for applying AC signals having the samefrequency but with mutually shifted phases is not limited thereto.

FIG. 11 is a circuit diagram illustrating the configuration of a delaycircuit. As shown in FIG. 11, the liquid crystal device 100 may beconfigured including a delay circuit 150 having a delay element 151provided between the routing wire 135 and the routing wire 136 and adelay element 151 provided between the routing wire 136 and the routingwire 137. A circuit configuration including a capacitance element (C)and an inductor element (L), a circuit configuration including aresistance (R) and a capacitance element (C), and so on can be given asexamples of the delay elements 151. According to the delay circuit 150,a first AC signal is applied to the first electrode 131 via the routingwire 135 as a result of the first AC signal being supplied to theexternal connection terminal 104 (It1). Likewise, a second AC signal,whose phase is shifted from the first AC signal, is applied to thesecond electrode 132 via the routing wire 136 as a result of the firstAC signal being transmitted to the routing wire 136 via the delayelement 151. Furthermore, a third AC signal, whose phase is shifted fromthe second AC signal, is applied to the third electrode 133 via therouting wire 137 as a result of the second AC signal being transmittedto the routing wire 137 via the delay element 151.

Accordingly, it is only necessary to generate the first AC signal in anexternal circuit and supply that signal to the external connectionterminal 104 (It1), which makes it possible to simplify the circuitconfiguration of the device as a whole.

According to the liquid crystal device 100 and the driving methodthereof in the first embodiment described thus far, the followingeffects are achieved.

1. The ion trapping mechanism 130 is provided between the electricityparting portion 120 and the sealant 40, and AC signals having the samefrequency but whose phases in an amount of time corresponding to asingle cycle are shifted relative to each other are applied to the firstelectrode 131, the second electrode 132, and the third electrode 133,respectively. Accordingly, the distribution of an electrical fieldgenerated between the ion trapping electrodes 131, 132, and 133 isscrolled from the first electrode 131 to the third electrode 133, and asa result of the electrical field scrolling, ionic impurities within theliquid crystal layer 50 are swept away from the display region E andinto the parting region E3 in which the ion trapping electrodes 131,132, and 133 are disposed.

2. The frequency f of the AC signals applied to the ion trappingelectrodes 131, 132, and 133, respectively, is derived from theaforementioned Formula (6), and is set to no more than 12 Hz, which islower than the frequency of an image signal (a driving signal) at thepixels P (for example, 60 Hz), in the case where the temperature is anormal temperature. In the case where the movement velocity v of theionic impurities in the liquid crystal layer 50 and the temperature of60° C. occurring when the device is actually used, the frequency f isset to no more than approximately 113 Hz. Accordingly, the ionicimpurities can be swept away to the parting region E3 with certainty.

3. A gap between the first electrode 131 of the ion trapping mechanism130 and the dummy pixel electrodes 121 of the electricity partingportion 120 is greater than a gap between the first electrode 131 andthe second electrode 132. Accordingly, it is difficult for the movementof the ionic impurities to be inhibited by an electrical field producedbetween the first electrode 131 and the dummy pixel electrodes 121, andthus the ionic impurities can be moved from the first electrode 131 tothe second electrode 132 smoothly.

4. The common electrode 23 is not provided in areas opposing the iontrapping electrodes 131, 132, and 133 on the opposite side of the liquidcrystal layer 50. Accordingly, it is difficult for an electrical fieldto be produced between the ion trapping electrodes 131, 132, and 133 andthe common electrode 23, and thus the ionic impurities can be swept awayto the parting region E3 with certainty by the electrical fieldscrolling produced between the ion trapping electrodes 131, 132, and133.

5. The parting portion 21, which has light-blocking properties, isprovided in the parting region E3, and thus even if ionic impurities areswept into and accumulate in the parting region E3 and the opticalproperties of the liquid crystal layer 50 in the parting region E3change as a result, the display in the display region E, which includesthe electricity parting portion 120, is not affected.

Second Embodiment

Next, a liquid crystal device according to a second embodiment will bedescribed with reference to FIG. 12. FIG. 12 is a cross-sectional viewillustrating the overall structure of the liquid crystal deviceaccording to the second embodiment. Note that FIG. 12 is a generalcross-sectional view corresponding to that shown in FIG. 6 and describedin the first embodiment. In the liquid crystal device according to thesecond embodiment, the common electrode 23 in the opposing substrate 20is disposed in a different manner than in the liquid crystal device 100according to the first embodiment. Configurations that are the same asthose in the first embodiment are given the same reference numerals, anddetailed descriptions thereof will be omitted.

As shown in FIG. 12, a liquid crystal device 200 according to the secondembodiment includes the liquid crystal layer 50, provided in a gapbetween an element substrate 210 and an opposing substrate 220 that areaffixed to each other using the sealant 40.

The pixel electrodes 15, the dummy pixel electrodes 121 and 122, and theion trapping electrodes 131, 132, and 133 are each disposed upon thethird interlayer insulating film 14 of the element substrate 210.

In the opposing substrate 220, the common electrode 23 is formed so asto span across the display region E and the parting region E3. In otherwords, the ion trapping electrodes 131, 132, and 133 and the commonelectrode 23 are disposed so as to oppose each other, with the liquidcrystal layer 50 interposed therebetween, in the parting region E3.

As in the first embodiment, AC signals having the same frequency butmutually different phases in an amount of time corresponding to a singlecycle (for example, the square waves indicated in FIG. 7) are applied tothe ion trapping electrodes 131, 132, and 133, respectively. As such, anelectrical field is produced between the first electrode 131 and thecommon electrode 23, as indicated by the solid-line or dotted-linearrows, depending on the polarity of the first potential at the firstelectrode 131. An electrical field is also produced between the secondelectrode 132 and third electrode 133 and the common electrode 23 in thesame manner as with the first electrode 131, as indicated by thesolid-line or dotted-line arrows. Because the AC signals having mutuallydifferent phases are applied to the ion trapping electrodes 131, 132,and 133, these electrical fields indicated by the solid-line ordotted-line arrows are scrolled, over time, from the first electrode131, which is closest to the display region E, toward the thirdelectrode 133.

Compared to the liquid crystal device 100 according to the firstembodiment, the liquid crystal device 200 according to the secondembodiment is affected by the strength of the electrical fields due tothe thickness of the liquid crystal layer 50; however, as in the firstembodiment, the ionic impurities in the display region E can be sweptaway to the parting region E3 by the ion trapping mechanism 130.

In addition, it is not necessary to perform patterning for causing thecommon electrode 23 to correspond to the display region E and providethe lead wires 23 a as in the liquid crystal device 100 according to thefirst embodiment, and thus the liquid crystal device 200 has anadvantage in that the configuration of the device can be simplified.

Third Embodiment

Next, a liquid crystal device according to a third embodiment will bedescribed with reference to FIG. 13. FIG. 13 is a cross-sectional viewillustrating the overall structure of the liquid crystal deviceaccording to the third embodiment. Unlike the liquid crystal device 100according to the first embodiment, which is transmissive, the liquidcrystal device according to the third embodiment is reflective.Configurations that are the same as those in the first embodiment aregiven the same reference numerals, and detailed descriptions thereofwill be omitted.

Like the liquid crystal device 100 according to the first embodiment, aliquid crystal device 300 according to the third embodiment includes theactive display region E1 in which the plurality of pixels P aredisposed, the dummy pixel region E2 in which the plurality of dummypixels DP are disposed, and the parting region E3 in which the partingportion 21 and the ion trapping mechanism 130 are disposed.

As shown in FIG. 13, pixel electrodes 15R of an element substrate 310are formed upon the third interlayer insulating film 14 from, forexample, Al (aluminum), an alloy containing Al, or the like thatreflects light. Each pixel electrode 15R is also electrically connectedto the second capacitance electrode 16 c of the storage capacitance 16via the contact hole CNT5 provided in the third interlayer insulatingfilm 14.

An inorganic insulating film 19 is formed so as to cover the pixelelectrodes 15R. The orientation layer 18, which is configured of acollection of the columns 18 a grown by deposing silicon oxide at anangle, is formed on the surface of the inorganic insulating film 19.

An inorganic insulating film 25 is formed so as to cover the commonelectrode 23, which is formed using a transparent conductive film suchas an ITO film on an opposing substrate 320. The orientation layer 24,which is configured of a collection of the columns 24 a grown bydeposing silicon oxide at an angle, is formed on the surface of theinorganic insulating film 25.

The liquid crystal layer 50, which is configured of the liquid crystalmolecules LC having a negative dielectric anisotropy, is interposedbetween the element substrate 310 on which the orientation layer 18 isformed and the opposing substrate 320 on which the orientation layer 24is formed.

The inorganic insulating films 19 and 25 are formed by deposing siliconoxide, for example. Covering the surface of the pixel electrodes 15R,whose work function differs from the common electrode 23, with theinorganic insulating film 19, and then covering the surface of thecommon electrode 23 with the inorganic insulating film 25 make itpossible to ameliorate a problem where the common potential (LCCOM)changes (shifts) due to differences in the work function when theinorganic insulating films 19 and 25 are not present.

The ion trapping electrodes 131, 132, and 133 are formed in the samelayer as the pixel electrodes 15R. Accordingly, the ion trappingelectrodes 131, 132, and 133 are also covered by the inorganicinsulating film 19. As in the first embodiment, AC signals that shiftbetween a high potential and a low potential with the common potential(LCCOM) of the common electrode 23 serving as a reference potential, andwhose phases in an amount of time corresponding to a single cycle areshifted relative to each other are applied to the ion trappingelectrodes 131, 132, and 133, and thus it is more difficult for a dropin the potential to be caused by the presence of the inorganicinsulating films 19 and 25 than in the case where a DC potential isapplied to the ion trapping electrodes 131, 132, and 133. Accordingly,the reflective liquid crystal device 300 that is capable of sweepingaway ionic impurities from the display region E to the parting region E3with certainty can be provided. Note that like the liquid crystal device100 according to the first embodiment, the common electrode 23 of theopposing substrate 320 is formed so as to span across the display regionE, and is not formed in the parting region E3. In other words, the iontrapping electrodes 131, 132, and 133 and the common electrode 23 arenot disposed so as to oppose each other with the liquid crystal layer 50interposed therebetween.

Fourth Embodiment Electronic Device

Next, a projection-type display apparatus serving as an electronicdevice according to a fourth embodiment will be described with referenceto FIG. 14. FIG. 14 is a schematic diagram illustrating theconfiguration of a projection-type display apparatus according to thefourth embodiment.

As shown in FIG. 14, a projection-type display apparatus 1000 serving asan electronic device according to this embodiment includes a polarizedillumination device 1100 disposed along a system optical axis L, twodichroic mirrors 1104 and 1105 serving as optical separating elements,three reflective mirrors 1106, 1107, and 1108, five relay lenses 1201,1202, 1203, 1204, and 1205, three transmissive liquid crystal lightvalves 1210, 1220, and 1230 serving as optical modulation units, a crossdichroic prism 1206 serving as a light synthesizing element, and aprojection lens 1207.

The polarized illumination device 1100 is generally configured of a lampunit 1101 that serves as a light source and is configured of a whitelight source such as an ultra-high-pressure mercury lamp, a halogenlamp, or the like, an integrator lens 1102, and a polarizationconversion element 1103.

Of a polarized light flux emitted from the polarized illumination device1100, the dichroic mirror 1104 reflects red (R) light and transmitsgreen (G) and blue (B) light. The other dichroic mirror 1105 reflectsthe green (G) light and transmits the blue (B) light, which have passedthrough the dichroic mirror 1104.

The red (R) light reflected by the dichroic mirror 1104 enters theliquid crystal light valve 1210 via the relay lens 1205 after beingreflected by the reflective mirror 1106.

The green (G) light reflected by the dichroic mirror 1105 enters theliquid crystal light valve 1220 via the relay lens 1204.

The blue (B) light transmitted by the dichroic mirror 1105 enters theliquid crystal light valve 1230 via an optical guide configured of thethree relay lenses 1201, 1202, and 1203 and the two reflective mirrors1107 and 1108.

The liquid crystal light valves 1210, 1220, and 1230 are disposed so asto face respective planes of incidence of each color of light in thecross dichroic prism 1206. The colored light that has entered the liquidcrystal light valves 1210, 1220, and 1230 is modulated based on imageinformation (image signals) and is emitted toward the cross dichroicprism 1206. This prism is formed by affixing four right-angle prisms,with a dielectric multilayer film that reflects red light and adielectric multilayer film that reflects blue light being formed in across shape on inner surfaces thereof. The three colors of light aresynthesized by these dielectric multilayer films, forming light thatexpresses a color image. The synthesized light is projected onto ascreen 1300 by the projection lens 1207, which is a projecting opticalsystem, and an image is displayed in an enlarged manner as a result.

The liquid crystal light valve 1210 employs the liquid crystal device100 according to the first embodiment or the liquid crystal device 200according to the second embodiment, which include the aforementioned iontrapping mechanism 130. A pair of polarizing elements are disposed, witha gap therebetween, in a cross Nicol pattern on the entry and exit sidesof the colored light in the liquid crystal panel 110. The same appliesto the liquid crystal light valves 1220 and 1230.

According to this projection-type display apparatus 1000, theaforementioned liquid crystal device 100 or liquid crystal device 200 isused as the liquid crystal light valves 1210, 1220, and 1230, and thus aprojection-type display apparatus 1000 that ameliorates display problemscaused by ionic impurities and provides superior display quality can beprovided.

Fifth Embodiment Electronic Device

Next, a projection-type display apparatus serving as an electronicdevice according to a fifth embodiment will be described with referenceto FIG. 15. FIG. 15 is a schematic diagram illustrating theconfiguration of a projection-type display apparatus according to thefifth embodiment.

As shown in FIG. 15, a projection-type display apparatus 2000 serving asan electronic device according to this embodiment includes a polarizedillumination device 2100 disposed along the system optical axis L, threedichroic mirrors 2111, 2112, and 2115, two reflective mirrors 2113 and2114, three reflective liquid crystal light valves 2250, 2260, and 2270serving as optical modulation units, a cross dichroic prism 2206, and aprojection lens 2207.

The polarized illumination device 2100 is generally configured of a lampunit 2101 that serves as a light source and is configured of a whitelight source such as a halogen lamp or the like, an integrator lens2102, and a polarization conversion element 2103.

A polarized light flux emitted from the polarized illumination device2100 is incident on the dichroic mirror 2111 and the dichroic mirror2112 that are disposed orthogonal to each other. The dichroic mirror2111 that serves as an optical separating element reflects red (R) lightof the polarized light flux that is incident thereon. The dichroicmirror 2112 that serves as another optical separating element reflectsgreen (G) light and blue (B) light of the polarized light flux that isincident thereon.

The reflected red (R) light is again reflected by the reflective mirror2113 and enters the liquid crystal light valve 2250. Meanwhile, thereflected green (G) light and blue (B) light are again reflected by thereflective mirror 2114 and are then incident on the dichroic mirror 2115serving as an optical separating element. The dichroic mirror 2115reflects the green (G) light and transmits the blue (B) light. Thereflected green (G) light enters the liquid crystal light valve 2260.The transmitted blue (B) light enters the liquid crystal light valve2270.

The liquid crystal light valve 2250 includes a reflective liquid crystalpanel 2251 and a wire grid polarization plate 2253 serving as areflective polarizing element.

The liquid crystal light valve 2250 is disposed so that the red (R)light reflected by the wire grid polarization plate 2253 is incidentvertically on the plane of incidence of the cross dichroic prism 2206.Furthermore, an auxiliary polarization plate 2254 that modifies thedegree of polarization of the wire grid polarization plate 2253 isdisposed on the side of the liquid crystal light valve 2250 on which thered (R) light enters, and another auxiliary polarization plate 2255 isdisposed on the light exit side of the red (R) light, along the plane ofincidence of the cross dichroic prism 2206. Note that the pair ofauxiliary polarization plates 2254 and 2255 can be omitted in the casewhere a polarizing beam splitter is used as the reflective polarizingelement.

The configuration of this reflective liquid crystal light valve 2250 andthe arrangement of the respective constituent elements thereof is thesame in the other reflective liquid crystal light valves 2260 and 2270.In other words, the liquid crystal light valve 2260 includes areflective liquid crystal panel 2261 and a wire grid polarization plate2263, an auxiliary polarization plate 2264 is disposed on the side ofthe wire grid polarization plate 2263 on which the green (G) light isincident, and another auxiliary polarization plate 2265 is disposed onthe side of the wire grid polarization plate 2263 from which the green(G) light exits, along the plane of incidence of the cross dichroicprism 2206.

Likewise, the liquid crystal light valve 2270 includes a reflectiveliquid crystal panel 2271 and a wire grid polarization plate 2273, anauxiliary polarization plate 2274 is disposed on the side of the wiregrid polarization plate 2273 on which the blue (B) light is incident,and another auxiliary polarization plate 2275 is disposed on the side ofthe wire grid polarization plate 2273 from which the blue (B) lightexits, along the plane of incidence of the cross dichroic prism 2206.

The respective color lights that enter the liquid crystal light valves2250, 2260, and 2270 are modulated based on image information, and onceagain enter the cross dichroic prism 2206 via the wire grid polarizationplates 2253, 2263, and 2273. The respective color lights are synthesizedby the cross dichroic prism 2206, the synthesized light is projectedonto a screen 2300 by the projection lens 2207, and an image isdisplayed in an enlarged manner as a result.

In this embodiment, the reflective liquid crystal device 300 accordingto the aforementioned third embodiment is employed as the liquid crystallight valves 2250, 2260, and 2270.

According to the projection-type display apparatus 2000, the reflectiveliquid crystal device 300 is used as the liquid crystal light valves2250, 2260, and 2270; as a result, a bright image can be projected,display problems caused by ionic impurities can be ameliorated, and thereflective projection-type display apparatus 2000 having superiordisplay quality can be provided.

The invention is not intended to be limited to the aforementionedembodiments, and many suitable changes can be made thereto withoutdeparting from the essence or spirit of the invention as set forth inthe appended aspects of the invention and the specification as a whole;driving methods for liquid crystal devices and electronic devices thatapply such liquid crystal devices derived from such modifications alsofall within the technical scope of the invention. Many variations canalso be considered in addition to the aforementioned embodiments.Several such variations will be described hereinafter.

First Variation

The locations where the ion trapping electrodes 131, 132, and 133 aredisposed in the liquid crystal device 100 according to theaforementioned first embodiment are not limited to those describedabove. FIG. 16 is a cross-sectional view illustrating the overallstructure of a liquid crystal device according to a first variation.Note that FIG. 16 corresponds to FIG. 6, which is referred to in thefirst embodiment. Constituent elements that are the same as those in theliquid crystal device 100 according to the first embodiment are giventhe same reference numerals, and detailed descriptions thereof will beomitted.

As shown in FIG. 16, a liquid crystal device 400 according to the firstvariation includes a liquid crystal layer 450 having positive dielectricanisotropy interposed between an element substrate 410 and an opposingsubstrate 420.

Pixels disposed in the active display region E1 of the element substrate410 include first pixel electrodes 15 a provided upon the thirdinterlayer insulating film 14 and connected to the TFTs 30 and secondpixel electrodes 15 b provided in a layer below the first pixelelectrodes 15 a and to which the common potential (LCCOM) is supplied.

Dummy pixels disposed in the dummy pixel region E2 of the elementsubstrate 410 include first dummy pixel electrodes 421 a provided uponthe third interlayer insulating film 14 and connected to the TFTs 30 andsecond dummy pixel electrodes 421 b provided in a layer below the firstdummy pixel electrodes 421 a and to which the common potential (LCCOM)is supplied. The first dummy pixel electrodes 421 a and the second dummypixel electrodes 421 b function as an electricity parting portion 120.

An ion trapping mechanism 430 disposed in the parting region E3 of theelement substrate 410 includes a first electrode 431, a second electrode432, and a third electrode 433 provided in the same layer as the firstpixel electrodes 15 a and the first dummy pixel electrodes 421 a, and afourth electrode 434 provided in a layer below the ion trappingelectrodes 431, 432, and 433 so as to oppose the ion trapping electrodes431, 432, and 433 and to which the common potential (LCCOM) is supplied.

Electrodes are not provided on the side of the opposing substrate 420that faces the liquid crystal layer 450.

Although not shown in FIG. 16, the first pixel electrodes 15 a, thefirst dummy pixel electrodes 421 a, the ion trapping electrodes 431,432, and 433, and the surface of the opposing substrate 420 that facesthe liquid crystal layer 450 are covered by an organic orientationlayer. Liquid crystal molecules having positive dielectric anisotropyare oriented approximately horizontally relative to the organicorientation layer.

The liquid crystal device 400 employs what is known as FFS (Fringe FieldSwitching), in which light incident on the pixels is modulated by usingan approximately horizontal electrical field produced between the firstpixel electrodes 15 a and the second pixel electrodes 15 b to change theorientation direction of the liquid crystal molecules in the liquidcrystal layer 450.

AC signals having the same frequency but whose phases are shiftedrelative to each other are applied to the ion trapping electrodes 431,432, and 433, respectively, so that an approximately horizontalelectrical field produced between the ion trapping electrodes 431, 432,and 433 and the fourth electrode 434 is scrolled from the firstelectrode 431, which is closest to the first dummy pixel electrodes 421a, toward the third electrode 433. Positive-polarity (+) ornegative-polarity (−) ionic impurities within the liquid crystal layer450 in the display region E are pulled toward the ion trappingelectrodes 431, 432, and 433, and are furthermore swept away to theparting region E3 by the stated electrical field scrolling.

Second Variation

The locations where the ion trapping electrodes 131, 132, and 133 aredisposed in the liquid crystal device 100 according to theaforementioned first embodiment are not limited to those describedabove. FIG. 17 is a cross-sectional view illustrating the overallstructure of a liquid crystal device according to a second variation.Note that FIG. 17 corresponds to FIG. 6, which is referred to in thefirst embodiment. Constituent elements that are the same as those in theliquid crystal device 100 according to the first embodiment are giventhe same reference numerals, and detailed descriptions thereof will beomitted.

As shown in FIG. 17, in a liquid crystal device 500 according to thesecond variation, an ion trapping mechanism 530 is provided in theparting region E3, between the dummy pixel region E2 where theelectricity parting portion 120 is disposed and the sealant 40. The iontrapping mechanism 530 includes a first electrode 531, a secondelectrode 532, and a third electrode 533 that are each provided in thesame layer as the common electrode 23 of an opposing substrate 520.

AC signals having the same frequency but whose phases in an amount oftime corresponding to a single cycle are shifted relative to each otherare applied to the ion trapping electrodes 531, 532, and 533,respectively. Positive-polarity (+) or negative-polarity (−) ionicimpurities within the liquid crystal layer 50 in the display region Eare pulled toward the ion trapping electrodes 531, 532, and 533, and arefurthermore swept away to the parting region E3 by electrical fieldscrolling produced between the ion trapping electrodes 531, 532, and533.

Although not shown in FIG. 17, it should be noted that the pixelelectrodes 15 and the dummy pixel electrodes 121 and 122 are covered bythe orientation layer 18. The common electrode 23, the first electrode531, the second electrode 532, and the third electrode 533 are coveredby the orientation layer 24. The liquid crystal layer 50 has negativedielectric anisotropy.

The common electrode 23 and the ion trapping electrodes 531, 532, and533 are each electrically connected to an external connection terminalprovided in a terminal unit of an element substrate 510, through anupper limit conductive portion provided between the element substrate510 and the opposing substrate 520.

Third Variation

In the liquid crystal device 100 according to the first embodiment, theion trapping electrodes 131, 132, and 133 are not limited to beingdisposed so as to surround the display region E. In the case where areaswhere display problems will occur due to the localization of ionicimpurities can be identified as shown in FIG. 4, the ion trappingelectrodes 131, 132, and 133 may be disposed so as to correspond to theareas where such display problems will occur.

Fourth Variation

The liquid crystal devices in which the ion trapping mechanisms 130,330, and 430 according to the aforementioned embodiments can be appliedare not limited to VA types or FFS types, and can also be applied in IPS(In Plane Switching), OCB (Optically Compensated Birefringence), andother such types as well.

Fifth Variation

The electronic device in which the liquid crystal device 100 accordingto the first embodiment or the liquid crystal device 200 according tothe second embodiment can be applied is not limited to theprojection-type display apparatus 1000 according to the fourthembodiment. Likewise, the electronic device in which the liquid crystaldevice 300 according to the third embodiment can be applied is notlimited to the projection-type display apparatus 2000 according to thefifth embodiment. The liquid crystal devices can be used favorably asthe display units of projection-type HUDs (heads-up displays) anddirect-view HMDs (head-mounted displays), information terminal devicessuch as electronic books, personal computers, digital still cameras,liquid crystal televisions, viewfinder-based or direct-viewmonitor-based video recorders, car navigation systems, electronicorganizers, POSs, and so on.

The entire disclosure of Japanese Patent Application No. 2013-126339,filed Jun. 17, 2013 is expressly incorporated by reference herein.

What is claimed is:
 1. A liquid crystal device driving method, theliquid crystal device including: a first substrate and a secondsubstrate that are disposed opposing each other and are laminated toeach other using a sealant; a liquid crystal layer interposed betweenthe first substrate and the second substrate; a pixel electrode providedin a display region of the first substrate; an opposing electrodeprovided in the first substrate or the second substrate so as to opposethe pixel electrode; and a first electrode that, when viewed from above,is provided between the display region and the sealant and to which afirst potential is supplied, a second electrode that, when viewed fromabove, is provided between the first electrode and the sealant and towhich a second potential is supplied, and a third electrode that, whenviewed from above, is provided between the second electrode and thesealant and to which a third potential is supplied, the first electrode,the second electrode, and the third electrode being provided in thefirst substrate or the second substrate, and the second electrode isprovided between the first electrode and the third electrode in a samelayer as the first electrode and third electrode, such that the firstelectrode, the second electrode, and the third electrode do not overlapeach other when viewed from above, the method comprising applying ACsignals having the same frequency to the first electrode, the secondelectrode, and the third electrode, respectively, so that: the secondpotential shifts from a positive-polarity or a reference potential to anegative-polarity after the first potential has shifted from thepositive-polarity or the reference potential to the negative-polaritybut before the first potential shifts to the reference potential or thepositive-polarity; the third potential shifts from the positive-polarityor the reference potential to the negative-polarity after the secondpotential has shifted to the negative-polarity but before the secondpotential shifts to the reference potential or the positive-polarity;the second potential shifts from the negative-polarity or the referencepotential to the positive-polarity after the first potential has shiftedfrom the negative-polarity or the reference potential to thepositive-polarity but before the first potential shifts to the referencepotential or the negative-polarity; and the third potential shifts fromthe negative-polarity or the reference potential to thepositive-polarity after the second potential has shifted from thenegative-polarity or the reference potential to the positive-polaritybut before the second potential shifts to the reference potential or thenegative-polarity.
 2. The driving method for a liquid crystal deviceaccording to claim 1, wherein a frequency f (Hz) of the AC signalsfulfils the following formula:f≦2μV _(E) /np ² where μ represents a degree of movement (m²/V·s) ofionic impurities in the liquid crystal layer, V_(E) represents aneffective voltage (V) of the AC signals, n represents a number ofelectrodes to which the AC signals are applied, and p represents a pitch(m) at which the electrodes to which the AC signals are applied aredisposed.
 3. The driving method for a liquid crystal device according toclaim 1, wherein the AC signals applied to the first electrode, thesecond electrode, and the third electrode, respectively, have the samewaveform.
 4. The driving method for a liquid crystal device according toclaim 3, wherein the AC signals have a potential of equal to threevalues or more than three values.
 5. The driving method for a liquidcrystal device according to claim 3, wherein the AC signals are squarewaves.
 6. An electronic device comprising: a liquid crystal devicedriven using the driving method for a liquid crystal device according toclaim
 1. 7. A liquid crystal device comprising: a first substrate and asecond substrate that are disposed opposing each other and are laminatedto each other using a sealant; a liquid crystal layer interposed betweenthe first substrate and the second substrate; a pixel electrode providedin a display region of the first substrate; an opposing electrodeprovided in the first substrate or the second substrate so as to opposethe pixel electrode; and a first electrode that, when viewed from above,is provided between the display region and the sealant and to which afirst potential is supplied, a second electrode that, when viewed fromabove, is provided between the first electrode and the sealant and towhich a second potential is supplied, and a third electrode that, whenviewed from above, is provided between the second electrode and thesealant and to which a third potential is supplied, the first electrode,the second electrode, and the third electrode being provided in thefirst substrate or the second substrate, wherein AC signals having thesame frequency are applied to the first electrode, the second electrode,and the third electrode, respectively, so that the second potentialshifts from a positive-polarity or a reference potential to anegative-polarity after the first potential has shifted from thepositive-polarity or the reference potential to the negative-polaritybut before the first potential shifts to the reference potential or thepositive-polarity; the third potential shifts from the positive-polarityor the reference potential to the negative-polarity after the secondpotential has shifted to the negative-polarity but before the secondpotential shifts to the reference potential or the positive-polarity;the second potential shifts from the negative-polarity or the referencepotential to the positive-polarity after the first potential has shiftedfrom the negative-polarity or the reference potential to thepositive-polarity but before the first potential shifts to the referencepotential or the negative-polarity; the third potential shifts from thenegative-polarity or the reference potential to the positive-polarityafter the second potential has shifted from the negative-polarity or thereference potential to the positive-polarity but before the secondpotential shifts to the reference potential or the negative-polarity;and the second electrode is provided between the first electrode and thethird electrode in a same layer as the first electrode and the thirdelectrode, such that the first electrode, the second electrode, and thethird electrode do not overlap each other when viewed from above.
 8. Theliquid crystal device according to claim 7, further comprising: a delaycircuit into which is inputted a first AC signal serving as the ACsignal and from which are outputted a second AC signal whose phase isshifted relative to the phase of the first AC signal and a third ACsignal whose phase is shifted relative to the phases of the first ACsignal and the second AC signal.
 9. The liquid crystal device accordingto claim 7, wherein the first electrode, the second electrode, and thethird electrode are provided in the first substrate so as to surroundthe display region.
 10. The liquid crystal device according to claim 9,wherein the display region includes an electricity parting portionhaving a plurality of dummy pixel electrodes provided so as to surrounda plurality of the pixel electrodes; and a gap between the electricityparting portion and the first electrode is greater than a gap betweenthe first electrode and the second electrode.
 11. The liquid crystaldevice according to claim 7, wherein the opposing electrode is providedin the second substrate, and when viewed from above, an outer edge ofthe opposing electrode is located between the first electrode and thedisplay region.
 12. The liquid crystal device according to claim 7,wherein the first electrode, the second electrode, and the thirdelectrode are provided in the first substrate; and the opposingelectrode is provided in the second substrate in a region that, whenviewed from above, contains the display region and extends to a regionthat opposes the first electrode, the second electrode, and the thirdelectrode, the reference potential being applied to the opposingelectrode.
 13. The liquid crystal device according to claim 12, furthercomprising: a delay circuit into which is inputted a first AC signalserving as the AC signal and from which are outputted a second AC signalwhose phase is shifted relative to the phase of the first AC signal anda third AC signal whose phase is shifted relative to the phases of thefirst AC signal and the second AC signal.
 14. The liquid crystal deviceaccording to claim 12, wherein the first electrode, the secondelectrode, and the third electrode are provided in the first substrateso as to surround the display region.
 15. The liquid crystal deviceaccording to claim 14, wherein the display region includes anelectricity parting portion having a plurality of dummy pixel electrodesprovided so as to surround a plurality of the pixel electrodes; and agap between the electricity parting portion and the first electrode isgreater than a gap between the first electrode and the second electrode.16. The liquid crystal device according to claim 12, wherein the pixelelectrode, the opposing electrode, the first electrode, the secondelectrode, and the third electrode are each covered by an inorganicorientation layer.
 17. An electronic device comprising the liquidcrystal device according to claim
 12. 18. The liquid crystal deviceaccording to claim 7, wherein the pixel electrode, the opposingelectrode, the first electrode, the second electrode, and the thirdelectrode are each covered by an inorganic orientation layer.
 19. Theliquid crystal device according to claim 18, wherein the pixel electrodeis formed of a conductive film having a light-reflecting property; theopposing electrode is formed of a conductive film having alight-transmissive property; and an inorganic insulating film is formedbetween the pixel electrode and the inorganic orientation layer.
 20. Anelectronic device comprising: the liquid crystal device according toclaim 7.